Framerate tanking after computer has been running a while.

[Energize]

So I've had this strange issue for a while now where if I start up my computer I can play a game at say 70fps, but after a couple of days up time or so, sometimes a lot less, I can start the game and I will get maybe 40fps, as soon as I restart my computer the issue is resolved and the frame rate goes back up again.

Cpu use is low, committed memory is low, can't seem to find any reason why this would be happening, is this a known issue with windows 10?

 

[Energize]

I leave my computer on because I use it as a workstation, so I have loads of terminals open, ftp/sql/php server running etc all the time so it is a real hassle to restart and then start running all those apps again.

It happens in every game, so it's not specific to say Doom, I was thinking maybe it's a driver isssue?